Device for correcting teeth irregularities

ABSTRACT

A supplementary device is provided for sliding operation for use in a device for correcting teeth irregularities. The supplementary device abuts a bracket, and has a wire-engaging slit having the same shape as a slit in the bracket so that a wire engaged in the bracket can also be engaged in the slit. The supplementary device has a pair of protrusions which forms a T-shape. The projections are used to anchor a rubber band. The supplementary device is slidable along the wire and slides until stopped, for example by the bracket.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 08/115,055, filed Sep. 2,1993, now U.S. Pat. No. 5,474,447, which is a continuation-in-part ofapplication of Ser. No. 07/886,564, filed May 21, 1992, which is nowU.S. Pat. No. 5,271,733, issued Dec. 21, 1993, which is acontinuation-in-part of application Ser. No. 07/678,422, filed Apr. 1,1991, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a device for correcting teethirregularities (malalignment), and more particularly, to a correctingdevice which can correct malalignment with no need of tying a wire tobrackets.

A conventional correcting device has, for example, as shown in FIG. 21,brackets 52, a wire 53 and strings 54 for tying the brackets to thewire. Each bracket is provided with a slit (wire-engaging-slit) 51 forcatching the wire 53. The wire 53 is inserted through a series of theslits of the brackets 52, and is supported thereby.

The wire 53 has a generally round shape in cross section, and sometimesa square shape.

In use of the device, each bracket 52 is fixed on each tooth T of themalalignment. The wire 53 is inserted through the series of slits 51 ofbrackets 52, and then, the wire 53 is bent in such way that spring forceof the wire 53 is applied upon the teeth to correct the alignment, andthe wire is tied on the brackets by means of the strings 54 withutilizing grooves 55 in the side surfaces of the brackets 52.

In the conventional device, it is very complicated to fasten the wire 53to each bracket 52, and high skill is required, and moreover it takesmuch time perform the fastening work. Especially, during the correctionof malalignment, which may take a few months, the wire has to be changedto a new wire having higher elastic force several times, since theelastic force becomes weekend by gradually moving of the teeth.

Consequently, both the orthodontist and the patient complicated andlaborious procedure whenever the wire is changed.

Further, in case a correcting torque is applied against the bracket byutilizing a square sectional wire in order to correct an inclination ortwist of teeth, it is difficult to fasten the wire to the bracket, andhighly refined technique is required for fixing the wire such thattorque is sufficiently transmitted.

In addition, since the conventional wire is made of a metal, the wire isbright and conspicuous, and the appearance is bad in use. Further, usersmay have adverse feeling about the wire.

In the conventional device, special brackets having cylindrical shapeare used in order to fix both ends of the wire, and consequently, thepatient feels disconfort in the mouth.

A main object of the present invention is to delete the above-mentionedproblems and to provide a device for correcting teeth irregularities,which is easily attached to the teeth, facilitates changing a wire, andcreates less adverse feeling in use.

Another object of the present invention is to provide a device forcorrecting teeth irregularities by using a plastic wire which has highresistance to creeps and has large geometrical moment of inertia of itscross sectional area.

In the conventional correcting method, it is difficult to fix thebracket to the tooth, wherein a twisted angle, inclined degree and thelike are large and each shape is different, in the appropriate locationand angle.

Many kind of the bracket having different shapes of the surface to becontacted with the tooth have been conventionally prepared or processedin accordance with the shape of the tooth.

The object of the present invention is to provide a device forcorrecting teeth irregularities wherein the device corresponds to atooth one-to-one and can be easily installed by providing the bracketwith the base plate which can be easily processed so as to have a shapecorresponding to each tooth.

As the tooth to be corrected, there are such case where the tooth istwisted, inclined, oblique, or a clearance between teeth is large. Whenthe clearance between teeth is large, a sliding operation is required.When the twisted tooth is corrected, it sometimes happens that thesliding operation is required in the correcting step.

When one tooth is corrected by the sliding operation, the brackets whichare fixed to the other teeth are corded up by a resilient material suchas a rubber band to create the force of the sliding operation.

However, since the bracket is small (width is in the range from 1 to 5mm, length is in the range of 1 to 5 mm), the rubber band is difficultto engage and sometimes slips off.

The present invention provides a supplementary device wherein aninstallation and removal can be easily performed.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a device forcorrecting teeth irregularities comprising:

a bracket to be fixed on tooth, said bracket having a slit;

a base plate which is interposed between said bracket and each surfaceto be fixed to said tooth; and

a wire to be inserted into said slit and engaged with said bracket; saidbase plate having a thickness being in a range of 0.5 to 5 mm and saidbase plate baing composed of easily plastically derformable resin on asurface to be fixed to said tooth, and said base plate being capable offorming such that said bracket is inclined at an angle relative to thevertical direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view partly in section, showing a main part ofan embodiment of the correcting device of the present invention;

FIG. 2 is a schematic perspective view wherein a bracket in FIG. 1 isseen from the side of a base plate;

FIG. 3 is a sectional view illustrating a wire of the present invention;

FIG. 4 is a sectional view illustrating another embodiment of thepresent invention;

FIG. 5 is a sectional view illustrating yet another embodiment of thepresent invention;

FIG. 6 is a sectional view illustrating yet another embodiment of thepresent invention;

FIGS. 7(a)-7(i) are a schematic view illustrating an example of a methodfor installating the correcting device of FIG. 1;

FIG. 8 is a perspective view illustrating another embodiment of thebracket used in the present invention;

FIG. 9 is a sectional view illustrating yet another embodiment of thepresent invention;

FIG. 10 is a sectional view illustrating a combination of the bracketand the wire of the present invention;

FIG. 11 is a sectional view illustrating another combination of thebracket and the wire;

FIG. 12 is a perspective view partly in section, showing a main part ofthe supplementary device of the present invention;

FIG. 13 is a perspective view partly in section, showing main part of anexample showing a method for installating the supplementary device ofthe present invention;

FIG. 14 is a front view illustrating an installated state of thesupplementary device of the present invention;

FIG. 15 is a plan view illustrating an example of the installated stateof the correcting device using a supplementary device of the presentinvention;

FIG. 16 is a plan view illustrating another embodiment of thesupplementary device of the present invention;

FIG. 17 is a plan view illustrating yet another embodiment of thesupplementary device of the present invention;

FIG. 18 is a perspective view illustrating yet another embodiment of thesupplementary device of the present invention;

FIG. 19 is a perspective view partly in section, showing a main part ofan example showing a method for installating the wire of the presentinvention;

FIG. 20 is a plan view partly in section, showing a main part of anotherembodiment of the correcting device of the present invention; and

FIG. 21 is a perspective view illustrating an example of theconventional device for correcting teeth irregularities.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, construction of a correcting device of thepresent invention is explained hereinafter.

FIGS. 1 and 2 show a main part of a correcting device A which is anembodiment of the present invention. The numeral 2 shows bracketsattached to teeth T, and the numeral 4 shows a wire inserted throughslits (wire-engaging-slits) 3 of the brackets 2. In the embodiment ofFIG. 1, the correcting device A comprises the brackets 2 and the wire 4.

The bracket 2 has a flat base part 2a which is to be attached to thetooth T, and a pair of L-shaped nails 2b arranged on both the upper andthe lower ends of the base part 2a respectively, so that they are facingeach other. As a result, the pair of nail parts 2b build up a T-shapedslit 3 therebetween.

The bracket 2 can be made of dental alloy, ceramics, plastics or thelike.

As the plastics material, dental resin such as polymethyl methacrylate,polyoxymethylene, polycarbonate, and the like, which has high strength,less moisture absorption and anti-plastic-deformation even in a moistatmosphere at 80° C. are preferably used.

However, another synthetic resin such as polyolefin, polyvinyl chloride,polyester and the like can also be used. Further, various fibrous orpowdery fillers of ceramics, metal, glass and the like can be blended inthe above-mentioned polymeric materials.

Metalic brackets are preferably to be coated with ceramics or plasticsso as to become neutral color (i.e. white, cream, or the like).

The above-mentioned wire 4 can be made of the same material as thebracket. However, materials having high resistance to creepage(advancing deformation due to stress), low sliding frictionalcoefficient and high durability against various germs or dirt in mouthare more preferable.

For example, a plastic tape molded together with (a) plastic filamentssuch as various kinds of polyester filaments, (b) the above-mentionedplastic filaments which are reinforced by blending inorganic crystalpowder, organic powder, or inorganic or organic fine fibers, (c) glassfibers for core member, or the like can be preferably used.

Through various experiments, it is demonstrated that creep resistance(anti-creep strength) of bending stress of a plastic extruded wire oftenlessens due to extension of the wire.

Therefore, for instance, there is such a case that it is preferable thata plastic wire which is made by only extruding without extension, orwhich is obtained by extruding a plastic material, heating the extrudedwire to the recrystallizing temperature thereof, and by cooling andcuring. The mechanism of improving resistance to creep due to the heattreatment is not clear. However, it is considered that the directions ofmolecules of the plastics which has been oriented by extrusion becomerandom when they are crystallized (unoriented crystallizing: a statethat fine crystals are arranged in disorder) by the heat treatment. Forexample, as to polyester, preferable condition of thermal curing isapproximately 30 sec to 2 minutes at 160° C.

As shown in FIGS. 3 to 4, a shape of the wire 4, wherein wire has anelongated projection on one side of surface thereof and has a "T" likeshape in section, is employed. A geometrical moment of the inertia ofsuch the wire having the elongated projections and having a "T" likeshape in section 2 to 8 times as large as the wire which has arectangular shape in section. With respect to the above wire which hasthe projection, the tooth of the malalignment can be corrected inmultiple directions (three-dimensionally).

According to the present invention, the wire which has the projectionhas the shape in section as follows. A height of the protrusion rangespreferably from 0.1 to 1 when a widthwise length of the wire is 1. Whenthe wire has the rectangular shape (width is 1.5 mm, thickness is 0.3mm), the geometrical moment of the inertia of the wire is 0.0034 mm⁴. Onthe contrary, when the wire is provided with the elongated projection(height of the projection is 0.3 mm, width is 0.4 mm), the geometricalmoment of the inertia of the wire is 0.0128 mm⁴. When the wire isprovided with the elongated projection (height of the projection is 0.6mm, width is 0.4 mm), the geometrical moment of the inertia of the wireis 0.0423 mm⁴. Further, with respect to the wire having an elongatedgroove as shown in FIG. 5, the wire is preferably provided with thegroove, wherein width ranges from 0.1 to 0.5 mm and depth ranges from0.005 to 0.3 mm, substantially in the center of the other side of thesurface of the wire.

Further, as shown in FIG. 5, when a wire 4 having a groove 6 extendingalong a longitudinal direction of the wire is used, the wire can beeasily and straightly folded as shown in FIGS. 19 by means of fingers For the like.

With respect to the wire shown in FIG. 6, the wire is provided with twoelongated projections 5 on the one side of the surface of the wire andthe elongated groove 6 on the other side of the surface of the wire. Thewire may be provided with the groove between two projections.

Hereinafter, the function and manner of use of the above-mentionedcorrecting device is described.

Firstly, bracket 2 is adhered to each tooth T as shown in FIG. 20. Insuch case, in accordance with the judgement of a dentist, the posturesof brackets 2 are adjusted and lined in such manner that the springforce of the wire becomes useful for correcting the alignment of teeth,and fixed there by means of resin adhesive.

Next, the wire 4 is inserted through the series of slits 3 of thebrackets 2 in order as shown in FIG. 1. At the time, the wire 4 can beset by inserting the end portion thereof from a T-shaped side opening ofthe slit 3 which is adhered to the back tooth which is in the deepestsuch as a molar. However, since the clearance between adjacent brackets2 is narrow, it is convenient to insert the wire, and then to push thewire 4 in the slits 3 from the front openings thereof such that the wireis folded (FIG. 19) in the longitudinal direction by means of fingers For a pair of tweezers.

The wire 4 pushed in the brackets 2 returns to the original flat shapesoon due to elasticity thereof. And both side edges are caught with thenails 2b.

The wire 4 might be previously bent in a U-shape as shown in FIG. 20,and might be partially bent in smaller radius of curvature or ispartially deformed, inclined, twisted or the like at regionscorresponding to the teeth to be moved.

Only by inserting the wire 4 through all brackets 2 as shown in FIG. 20,is attaching of the correcting device is finished. That is to say, it isnot necessary to fasten the wire 4 to the brackets 2 with strings or thelike, since the wire 4 is securely caught by the nails 2b. In addition,it is not necessary to fix the ends of the wire 4 with special bracketshaving a cylindrical shape which is necessary in conventional manner sothat the wire 4 cannot slip along slits, in the brackets 2.

If the occasion arises, the ends of wire 4 might be folded and set withheat.

After installation of the wire 4, spring reaction force of the wire 4 istransmitted to the teeth Ta to be moved through the brackets 2.Consequently, the force (for example, about 20 to 200 g) shown in FIG.20 by an arrow N is applied to the teeth Ta for a long time. As aresult, the teeth Ta are moved in the direction of the arrow Ngradually.

And besides, when a correcting torque in the twisting direction isrequired, a suitable correcting torque can be applied by merely changingthe direction of the bracket 2, to be fixed on the tooth Ta, or bymerely changing the shape of curvature of the wire 4. As the tooth Tamoves and then the wire 4 returns back to the original shape thereof,the spring force, i.e. correcting force, becomes weaker. In suchcondition, only the wire is changed for a new one with high stiffness,leaving the brackets 2 as they are. The old wire can be easily removedby catching the end and drawing out of the slits. If required, the wirecan be previously cut into some pieces.

The new wire can be attached to the brackets 2 not only in such manneras shown in FIG. 19, but also by drawing out the old one afterconnecting with the old one.

The wire is generally changed about once per several weeks as occasiondemands. That is to say, during the whole treatment period, a half totwo years, the wire is changed several times.

In the above-mentioned embodiments, the brackets 2 are directly fixed onteeth as shown in FIG. 12.

However, it is more preferable that the bracket 2 is adhered to eachtooth T through a base plate 15.

In this case, as a material of the base plate 15, it is advantageous forthe device to employ material which is easily prepared. The base platecan be made from hard resin. The base plate is advantageously made fromeasily plastically deformable resin. The easily plastically deformableresin is a resin having a plasticity which is soft in beginning or whichbecomes plastic by applying heat. A thickness of the base plate rangesapproximately from 0.5 to 5 mm in consideration of workability.

Next, a function of the base plate, which is made from easilyplastically deformable resin, or the present invention will be explainedin accordance with FIG. 7. FIGS. 7 (a) to 7 (d) are schematic plan viewsillustrating working steps wherein molding is performed to the tooth Tato be corrected by using the base plate 15 and the base plate 15 isfixed to the tooth. The base plate 15 mounted on the base part 2a of thebracket 2 is abutted to the tooth (FIGS. 7(a) to 7(b)) to which thebracket 2 is fixed so that the base plate 15 is firmly molded. Since thebase plate 15 has easily plastic deformability, the base plate 15 can beeasily deformed and closely contacted with the surface of the tooth. Inorder that the base plate 15 is easily deformed, heat may be applied, ifdesired. When the material of the base plate does not have an adhesionproperty relative to the tooth, the molding work can be directly on thetooth of a patient without any pain. When the material of the base platehas the adhesion property relative to the tooth, or the tooth to becorrected is located in the place where molding work is hard to beperformed, teeth irregularities are molded by using a gypsum beforehand.

The molded base plate 5 together with the bracket 2 are removed from thetooth (FIG. 7(c)), then cured. With respect to the resin having curingproperty, as means for curing, the means which has been conventionallyused in the field of prosthodontia can be employed using heat, light,and the like. With respect to thermoplastic resin, the resin is cured bycooling.

As shown in FIG. 7 (d), the bracket 2 having the cured base plate 15 isfixed to the corresponding tooth Ta by means of an adhesive (not shown).In the conventional technique wherein the bracket is fixed to the toothby means of the adhesion, it is very difficult to adjust a quantity ofthe adhesive and a gap between the tooth and the bracket. On thecontrary, according to the present invention the bracket can be easilyfixed to the tooth with a slight adjustment. Further, there is sometimessuch a need that a tooth should be torqued around the axis extending inthe widthwise direction (Y-axis in FIG. 7(e)). In such the case,conventionally it is necessary to prepare a bracket wherein the bracketis formed in such a manner as to be inclined at desired angle (θ)relative to the vertical axis (Z-axis in FIG. 7(e)), or a bracket havinga slit which is digged at a certain angle (θ) relative to the Z-axis.Hence, by virtue of thus formed bracket, the wire inserted into the slitof the bracket can generate a torsional force.

On the contrary, in accordance with the present invention, it is notnecessary to prepare some brackets to have each different shapes inaccordance with a degree (θ) of torquring to be required since the baseplate can be readily formed to have a wedge like shape in the mouth by adentist in the dental curing as shown in FIG. 7(f).

Accordingly, all dental curing for correcting teeth irregularities totorque at any degrees can be achieved by employing only a single type ofthe bracket.

Normally, backside of teeth T are aligned in a horseshoe-like-shapedsmooth curve as shown in FIGS. 7 (g) to 7(i). Accordingly, if there is atooth which is spaced from the curve, it is required to correct teethirregularities such that the backside of the tooth Ta is aligned in thecurve. In that case, conventionally there has hitherto been a need toprepare many brackets, each of which base plate formed integrallytherewith has different thickness according to a distance spaced fromthe curve. In that case, the thickness of the base plate of the tooth Tamust be thicker than that of the other teeth T. Thereafter, the wirehaving a smooth and continuous horse-shoe-like shape is inserted intoeach of the brackets. Thereby, desired teeth alignment can be obtained.However, in accordance with the base plate of the present invention, itis not necessary to prepare many brackets having different thickness ofthe base plates but only one type of the brackets formed separately withthe base plate since the base plate can be readily made to have anythickness according to the distance spaced from the curve as shown inFIG. 7(i).

The wire is inserted into the slit of each bracket 2 which isrespectively fixed to the tooth so that the base plate of correctingteeth irregularities is created (FIG. 7(d)). The base plate which ismade from easily plastically deformable resin can be applied to not onlythe conventional bracket but also the bracket which uses the wire havinga rectangular shape in section.

The base plate is composed of the easily plastically deformable resin.As the easily plastically deformable resin, dental materials e.g.thermosetting resin such as epoxy resin, acrylic resin, phenolic resin,photocurable resin such as epoxy resin, acrylic ultraviolet crosslinkingresin, thermosetting resin such as polyolefin resin, polyester resin,polyamide resin, polyimide resin, polycarbonate resin, which areconventionally known, can be employed. The photocurable resin isobtained by mixing a base polymer (or monomer) such as polyfunctionalmethacrylate, methacrylate having a ulethane bond with a filler such apowder of quarts, glass, ceramics, silica, or combination thereof.

As the adhesives, the adhesives which is conventionally known may beselected in accordance with the materials of the base plate. Accordingto the present invention, the base plate has a surface wherein shape canbe closely contacted with the tooth so that the quantity of the adhesiveis not great, a processing or a modification after bonding is remarkablyreduced.

Next, a supplementary device for correcting teeth irregularities of thepresent invention will be concretely explained in accordance with FIG.12. The supplementary device is useful for a sliding operation of thetooth when the supplementary device is used together with theabove-mentioned correcting device (e.g. FIG. 14 or FIG. 15).

As shown in FIG. 12, the supplementary device 25 is provided with awire-engaging-slit 26 having substantially the same shape as the slit 3in the bracket so that the wire 4 is engaged with the slit 26. Theengaging state of the supplementary device is the same as that of thebracket and the supplementary device is allowed to slide in only thedirection along with the wire thereon. The slit 26 of the supplementarydevice 25 involves a nail part 25b and a base part 25a so that the slitis formed into a "T" shape. As shown in FIG. 12, the nail part 25b isprovided with a protrusion 27 having a projecting edge which isvertically exteding. As shown in FIG. 12, the nail part 25b may beprovided with two protrusions 27 in both the upper and the lowermarginal edges. The nail part 25b may have only one protrusion either inthe upper or the lower marginal edge. In any case, a force applied tothe tooth can be adjusted by selecting a location or combination of theprotrusion 27 (e.g. FIG. 14). An elastic material such as rubber band 28is engaged with the protrusion 27 so that a shrinkage force originatesbetween two supplementary devices (referring to FIG. 14) each of whichis stopped by the correcting device so as to be corded up.

Since the supplementary device 25 is slidable on the wire, the bracketplays the part as a stopper (FIGS. 13 and 14).

One feature of the present invention lies in that after the correctingdevice is once assembled and mounted on the tooth, the supplementarydevice is easily combined with the correcting device. That is to say,the wire 4 is pinched by a finger and a thumb so as to be bended (orfolded) in the widthwise direction, and the wire 4 is engaged with theslit 23 of the supplementary device 25 so that the supplementary device25 can be easily installed in the wire 4. Accordingly, when the twistedtooth is returned to the normal posture and subjected to a slidingoperation, installation and removal can be easily performed. In FIG. 14,a state of the supplementary device, which is installed by the rubberband 28 and combined with the bracket 2 and the wire 4, is illustrated.The rubber band 28 may be engaged with the protrusions 27 in parallelwith the wire. The rubber band may be engaged with the protrusiondiagonally. A schematic plan view of the supplementary device and thebracket, which are installed on the teeth, the illustrated in FIG. 15.

The supplementary device of the present invention can have several kindof features other than the device shown in FIG. 12.

For instance, as shown in FIG. 16, the supplementary device may have ashape, wherein the protrusion 27 is combined with a recessed portion 29,so that the rubber band is surely engaged with the protrusion. As shownin FIG. 17, the protrusion 27 may be formed on the nail part 25b near alocation wherein the bracket is to be contacted.

As shown in FIG. 18, the protrusion 27 may be shifted in the widthwisedirection. The force applied to the tooth can be adjusted by changingthe location of the protrusion. According to FIGS. 13 and 14, thesupplementary device is installed in the wire so that the base part isopposed to the tooth (the base part is on the reverse side).

The supplementary device can be installed in the wire so as to be turnedover. The protrusion is normally formed in side face 30 (FIG. 18) of thesupplementary device so as to be in the direction extending across thewire in consideration of a strength and an easiness of producing thesuplementary device. Any protrusion, wherein the rubber band can beengaged, may be employed. The supplementary device has preferably adimension as follows. A width is in the range from 2 to 6 mm, a lengthis in the range from 1 to 5 mm and a thickness is in the range from 1 to2 mm.

As the wire applied to the supplementary device, the wire havingrectangular shape in section as well as the wire having an elongatedprojection or a groove can be employed.

The supplementary device can be used so as not to be fixed to the tooth.However, the wire is not excluded from being used so as to be fixed tothe tooth. When the correction of the tooth is limited to the slidingoperation, the bracket can be provided with the protrusion. The sameeffect is achieved from the correction of the tooth point of view. Inthe view point of a diversity of using and a treatment, thesupplementary device is more advantageous.

The supplementary device can be made from the same materials as thebracket. Since the supplementary device is used for a relatively shortperiod and is seldom fixed to the tooth compared with the bracket, thestrength is not necessarily high. The base part can be relatively thin,then the supplementary device can be installed in the wire by bendingthe base part and opening the slit.

As mentioned above, the correcting device of the present invention hasan advantage that setting of the device and changing of a wire is veryeasy due to the shape of bracket and cross section of the wire.

Therefore, a synthetic resin with rather less in anti-creepage propertycan be used as a material of the wire, since such disadvantage can becompensated by adding frequency of change of wires.

Therefore, since various synthetic resins having clear or white colorcan be freely used as a material of the wire, the present invention cansatisfy a demand to use an incouspicuous wire.

According to the present invention, the bracket is firmly fixed to thetooth and a workability of installing the bracket on the tooth isimproved.

Though several embodiments of the invention are described above, it isto be understood that the present invention is not limied to theabove-mentioned embodiments, and various changes and modifications maybe made in the invention without departing from the spirit and scopethereof.

What we claim is:
 1. A device for correcting teeth irregularitiescomprising:a bracket on which is a slit having a T-shaped section; awire to be inserted into said slit and engaged with said bracket; asupplementary device for a sliding operation along said wire, saidsupplementary device comprising: a wire engaging slit havingsubstantially the same shape as said bracket slit; and at least oneprotrusion for engaging said bracket.